Generation of recombinant retroviruses encoding human cytokine genes. A series of retroviruses that express the cytokine genes and a selectable marker gene, were constructed and tested for the efficiency of transduction as well as stable expression of the cytokine genes. Insertion of cytokine genes into tumor infiltrating lymphocytes. The most efficient retroviral vector containing the human tumor necrosis gene was used to insert the TNF gene into several human TIL. The transduced TIL were extensively characterized for the stable integration and high phenotype, cytotoxicity, expression of other cytokines, and clonality using T-cell receptor gene rearrangements. A clinical protocol based on the use of TNF-gene modified TIL in cancer patients is currently under review. Insertion of cytokine genes into human and mouse tumors. Using retroviruses containing human TNF and IL-2 genes, we introduced the cytokine genes into mouse and human tumors and characterized the gene-modified tumors for the integration, expression, growth and other properties in vitro as well as th biological effects in vivo both in athymic and syngeneic animals. The gene transferred tumor cells were unable to form progressively growing tumors. T cytokine-gene transferred cells contained the intact proviral genome and expressed the cytokines in vivo. Significance. The significance of the project lies in therapeutic TIL based on cytokine gene transfer for the treatment of human cancers. One insertion of genes into tumors was to evaluate the effects of such gene insertions into animal models.